1. Field of the Invention
The present invention relates to a device for assembling a bone implant and the tool for positioning it and particularly to a coupling device which permits the tool and implant to be quickly assembled by axially adjustable shims which selectively lock axially oriented teeth carried by the tool with undercut notches formed in the face of the implant.
2. History of the Art
Bone implants such as artificial acetabula for the femur head, made of metal or plastic material, are known to be provided on their periphery with one or more threads of cylindrical, truncated or spherical form which are used to secure the implant in the bone.
Three systems for positioning such bone implants exist at the present time:
A first method requires that a prior tapping be made in the hip bone so that when the acetabulum is to be replaced, the prosthesis is screwed in position within the tapped opening;
In certain cases, the outer thread of the prosthesis is in the form of a tap so as to allow the prosthesis to be positioned or implanted directly in the bone.
In those instances where the prosthesis comprises a metallic element provided with a cup made of plastic material, the cup is placed in position after the metallic element is implanted in the bone.
The object of the improvements forming the subject matter of the present invention is to facilitate positioning or implanting of artificial acetabula.
Most systems for positioning known at present comprise an implantation element or handle which is freely movable with respect to the acetabulum, this making it impossible to accurately control the direction or orientation of the artificial acetabulum during the implantation operation.
In French Patent No. 77 20235 a system for fixing the artificial acetabulum is disclosed, in which assembly screws are used to join the implantation tool to the acetabulum employing a wrench. However, taking into account the operational conditions, this system is difficult to use and the parts are difficult to separate as such separation must be effected directly in the location of the joint or connection. Moreover, dismantling of the assembly by removal of the screws is a long operation, leading to a loss of time which is detrimental for the patient and for the overall efficiency of the operation.